backend: use generic instead of any type for test suite

internal/backend/b2/b2_test.go

@@ -16,13 +16,13 @@ import (
 	rtest "github.com/restic/restic/internal/test"
 )
 
-func newB2TestSuite(t testing.TB) *test.Suite {
+func newB2TestSuite(t testing.TB) *test.Suite[b2.Config] {
 	tr, err := backend.Transport(backend.TransportOptions{})
 	if err != nil {
 		t.Fatalf("cannot create transport for tests: %v", err)
 	}
 
-	return &test.Suite{
+	return &test.Suite[b2.Config]{
 		// do not use excessive data
 		MinimalData: true,
 
@@ -30,10 +30,10 @@ func newB2TestSuite(t testing.TB) *test.Suite {
 		WaitForDelayedRemoval: 10 * time.Second,
 
 		// NewConfig returns a config for a new temporary backend that will be used in tests.
-		NewConfig: func() (interface{}, error) {
+		NewConfig: func() (b2.Config, error) {
 			cfg, err := b2.ParseConfig(os.Getenv("RESTIC_TEST_B2_REPOSITORY"))
 			if err != nil {
-				return nil, err
+				return b2.Config{}, err
 			}
 
 			cfg.AccountID = os.Getenv("RESTIC_TEST_B2_ACCOUNT_ID")
@@ -43,20 +43,17 @@ func newB2TestSuite(t testing.TB) *test.Suite {
 		},
 
 		// CreateFn is a function that creates a temporary repository for the tests.
-		Create: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(b2.Config)
+		Create: func(cfg b2.Config) (restic.Backend, error) {
 			return b2.Create(context.Background(), cfg, tr)
 		},
 
 		// OpenFn is a function that opens a previously created temporary repository.
-		Open: func(config interface{}) (restic.Backend, error) {
-			cfg := config.(b2.Config)
+		Open: func(cfg b2.Config) (restic.Backend, error) {
 			return b2.Open(context.Background(), cfg, tr)
 		},
 
 		// CleanupFn removes data created during the tests.
-		Cleanup: func(config interface{}) error {
-			cfg := config.(b2.Config)
+		Cleanup: func(cfg b2.Config) error {
 			be, err := b2.Open(context.Background(), cfg, tr)
 			if err != nil {
 				return err